【小家Spring】如何证明Spring是存在父子容器的？顺便解决Spring MVC访问一直404问题（配置文件没问题）（下）

<!-- 注解的处理器映射器，他来解析RequestMapping，然后和处理器对应起来 -->
<bean   class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"></bean> 
<!-- 注解的处理器适配器 结合上面一起协作-->
<bean   class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"></bean> 

  @Override
  public void afterPropertiesSet() {
    this.config = new RequestMappingInfo.BuilderConfiguration();
    this.config.setUrlPathHelper(getUrlPathHelper());
    this.config.setPathMatcher(getPathMatcher());
    this.config.setSuffixPatternMatch(this.useSuffixPatternMatch);
    this.config.setTrailingSlashMatch(this.useTrailingSlashMatch);
    this.config.setRegisteredSuffixPatternMatch(this.useRegisteredSuffixPatternMatch);
    this.config.setContentNegotiationManager(getContentNegotiationManager());
    super.afterPropertiesSet();
  }
  //super.afterPropertiesSet();如下
  @Override
  public void afterPropertiesSet() {
    initHandlerMethods();
  }
  // 初始化处理器
  protected void initHandlerMethods() {
    String[] beanNames = (this.detectHandlerMethodsInAncestorContexts ?
        BeanFactoryUtils.beanNamesForTypeIncludingAncestors(obtainApplicationContext(), Object.class) :
        obtainApplicationContext().getBeanNamesForType(Object.class));
    //拿到所有的beanNames
    for (String beanName : beanNames) {
      if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) {
        Class<?> beanType = null;
        try {
          beanType = obtainApplicationContext().getType(beanName);
        }
        //这里很关键，这里表面 只处理标注了注解@Controller或者@RequestMapping的  就认为才是处理器  然后拿到里面的方法，每一个方法就是一个处理器
        if (beanType != null && isHandler(beanType)) {
          detectHandlerMethods(beanName);
        }
      }
    }
    handlerMethodsInitialized(getHandlerMethods());
  }
  @Override
  protected boolean isHandler(Class<?> beanType) {
    return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
        AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
  }

<!-- 备注：此句只写在Spring MVC的配置文件里，否则出问题  Handler映射不上 -->
<mvc:annotation-driven></mvc:annotation-driven>

@ComponentScan(value = "com.fsx", excludeFilters = {
        @Filter(type = FilterType.ANNOTATION, classes = {Controller.class}),
        //排除掉web容器的配置文件，否则会重复扫描
        @Filter(type = FilterType.ASSIGNABLE_TYPE, classes = {AppConfig.class}),
        @Filter(type = FilterType.ASSIGNABLE_TYPE, classes = {WebMvcConfig.class}),
})
@Configuration
public class RootConfig { ... }

@ComponentScan(value = "com.fsx", useDefaultFilters = false,
        includeFilters = {@Filter(type = FilterType.ANNOTATION, classes = {Controller.class})}
)
@Configuration
@EnableWebMvc
public class AppConfig implements WebMvcConfigurer {
    @Bean
    public Child child() {
        return new Child();
    }
    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        MappingJackson2HttpMessageConverter messageConverter = new MappingJackson2HttpMessageConverter();
        messageConverter.setSupportedMediaTypes(Arrays.asList(MediaType.APPLICATION_JSON_UTF8));
        converters.add(new StringHttpMessageConverter(Charset.forName("UTF-8")));
        converters.add(messageConverter);
    }
}

    @ResponseBody
    @GetMapping("/hello")
    public String helloGet() {
        ApplicationContext ctx1 = WebApplicationContextUtils.getWebApplicationContext(request.getSession().getServletContext());
        //从controller从获取这个Bean 能获取到controller这个Bean吗
        // 用跟容器或者bean 直接报错org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type
        HelloController bean = ctx1.getBean(HelloController.class);
        System.out.println(bean);
}

    @Autowired
    private HelloController helloController;
    @ResponseBody
    @GetMapping("/hello")
    public String helloGet() {
        System.out.println(helloController == this); //true
        return "hello...Get";
    }

    private ApplicationContext context;
    @ResponseBody
    @GetMapping("/hello")
    public String helloGet() {
        System.out.println(context.getParent()); //Root WebApplicationContext: startup date [Sun Feb 24 21:49:25 CST 2019]; root of context hierarchy
        System.out.println(context.getBean(HelloController.class)); //com.fsx.controller.HelloController@32a2d798
        return "hello...Get";
    }

    @ResponseBody
    @GetMapping("/hello")
    public String helloGet() {
        //方法一
        ApplicationContext context = (ApplicationContext) request.getAttribute(DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE);
        ApplicationContext context1 = RequestContextUtils.findWebApplicationContext(request);
        //此处dispatcher为dispatcherServlet的默认名称
        ApplicationContext context2 = (ApplicationContext) request.getServletContext().getAttribute(FrameworkServlet.SERVLET_CONTEXT_PREFIX + "dispatcher");
        System.out.println(context == context1); //true
        System.out.println(context == context2); //true
        System.out.println(context.getBean(HelloController.class));
        return "hello...Get";
    }